Remove strip from ProceduralDataset::core score_answer() (#250)

* remove strip from ProceduralDataset::core score_answer(), strip in extract answer (optional, default=True)
* test: Move test_extract_answer() from test_dataset.py to test_utils.py
* refactor: Improve decimal reward computation with more flexible comparison
* fix: Implement rounding for format_number when round_if_needed is True
* test: Add test case for compute_decimal_reward with sign and zeros

tests/test_utils.py

@@ -0,0 +1,53 @@
+import pytest
+
+from reasoning_gym.utils import compute_decimal_reward, extract_answer, format_number
+
+
+def test_extract_answer():
+    assert extract_answer("This is a text. <final_answer>1234</final_answer>", tag_name="final_answer") == "1234"
+
+    # ignore whitespaces
+    assert extract_answer("This is a text. <answer>\n1234 </answer>", tag_name="answer", strip=True) == "1234"
+
+
+def test_format_number():
+    # Test integers
+    assert format_number(42) == "42"
+    assert format_number(42.0) == "42"
+
+    # Test decimals
+    assert format_number(3.14) == "3.14"
+    assert format_number(3.10) == "3.1"
+    assert format_number(3.00) == "3"
+
+    # Test with max_decimals (rounding)
+    assert format_number(3.14159, max_decimals=4, round_if_needed=True) == "3.1416"
+
+    # Test with trailing zeros
+    assert format_number(5.5000) == "5.5"
+
+    # Test error cases
+    with pytest.raises(ValueError):
+        format_number(3.14159, max_decimals=2)
+
+
+def test_compute_decimal_reward():
+    # Test exact matches
+    assert compute_decimal_reward("42", "42") == 1.0
+    assert compute_decimal_reward("3.14", "3.14") == 1.0
+
+    # Test with commas
+    assert compute_decimal_reward("1,000", "1000") == 1.0
+    assert compute_decimal_reward("1,000", "1000", strip_commas=False) < 1.0
+
+    # Test with sign, leading zeros, and trailing decimals
+    assert compute_decimal_reward("+0001,000.00", "1000") == 1.0
+
+    # Test partial matches
+    assert compute_decimal_reward("The answer is 42", "42") < 1.0
+    assert compute_decimal_reward("The answer is 42", "42") > 0.01
+
+    # Test invalid answers
+    assert compute_decimal_reward(None, "42") == 0.0
+    assert compute_decimal_reward("", "42") == 0.0
+    assert compute_decimal_reward("not a number", "42") == 0.01